kernel/linux.git/arch/x86/lib/delay.c, branch v7.0.10

x86/asm: Rename rep_nop() to native_pause()

2025-04-18T08:19:26+00:00

Rename rep_nop() function to what it really does. No functional change intended. Suggested-by: David Laight Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Cc: H. Peter Anvin Link: https://lore.kernel.org/r/20250418080805.83679-1-ubizjak@gmail.com

x86/delay: Fix inconsistent whitespace

2025-03-05T08:51:04+00:00

Smatch warns about this whitespace damage: arch/x86/lib/delay.c:134 delay_halt_mwaitx() warn: inconsistent indenting Signed-off-by: Charles Han Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20250305063515.3951-1-hanchunchao@inspur.com

arch/x86: Fix typos

2024-01-03T10:46:22+00:00

Fix typos, most reported by "codespell arch/x86". Only touches comments, no code changes. Signed-off-by: Bjorn Helgaas Signed-off-by: Ingo Molnar Reviewed-by: Randy Dunlap Link: https://lore.kernel.org/r/20240103004011.1758650-1-helgaas@kernel.org

x86/delay: Fix the wrong asm constraint in delay_loop()

2022-04-05T19:21:57+00:00

The asm constraint does not reflect the fact that the asm statement can modify the value of the local variable loops. Which it does. Specifying the wrong constraint may lead to undefined behavior, it may clobber random stuff (e.g. local variable, important temporary value in regs, etc.). This is especially dangerous when the compiler decides to inline the function and since it doesn't know that the value gets modified, it might decide to use it from a register directly without reloading it. Change the constraint to "+a" to denote that the first argument is an input and an output argument. [ bp: Fix typo, massage commit message. ] Fixes: e01b70ef3eb3 ("x86: fix bug in arch/i386/lib/delay.c file, delay_loop function") Signed-off-by: Ammar Faizi Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220329104705.65256-2-ammarfaizi2@gnuweeb.org

x86/delay: Introduce TPAUSE delay

2020-05-07T14:06:20+00:00

TPAUSE instructs the processor to enter an implementation-dependent optimized state. The instruction execution wakes up when the time-stamp counter reaches or exceeds the implicit EDX:EAX 64-bit input value. The instruction execution also wakes up due to the expiration of the operating system time-limit or by an external interrupt or exceptions such as a debug exception or a machine check exception. TPAUSE offers a choice of two lower power states: 1. Light-weight power/performance optimized state C0.1 2. Improved power/performance optimized state C0.2 This way, it can save power with low wake-up latency in comparison to spinloop based delay. The selection between the two is governed by the input register. TPAUSE is available on processors with X86_FEATURE_WAITPKG. Co-developed-by: Fenghua Yu Signed-off-by: Fenghua Yu Signed-off-by: Kyung Min Park Signed-off-by: Thomas Gleixner Reviewed-by: Tony Luck Link: https://lkml.kernel.org/r/1587757076-30337-4-git-send-email-kyung.min.park@intel.com

x86/delay: Refactor delay_mwaitx() for TPAUSE support

2020-05-07T14:06:19+00:00

Refactor code to make it easier to add a new model specific function to delay for a number of cycles. No functional change. Co-developed-by: Fenghua Yu Signed-off-by: Fenghua Yu Signed-off-by: Kyung Min Park Signed-off-by: Thomas Gleixner Reviewed-by: Tony Luck Link: https://lkml.kernel.org/r/1587757076-30337-3-git-send-email-kyung.min.park@intel.com

x86/delay: Preparatory code cleanup

2020-05-07T14:06:19+00:00

The naming conventions in the delay code are confusing at best. All delay variants use a loops argument and or variable which originates from the original delay_loop() implementation. But all variants except delay_loop() are based on TSC cycles. Rename the argument to cycles and make it type u64 to avoid these weird expansions to u64 in the functions. Rename MWAITX_MAX_LOOPS to MWAITX_MAX_WAIT_CYCLES for the same reason and fixup the comment of delay_mwaitx() as well. Mark the delay_fn function pointer __ro_after_init and fixup the comment for it. No functional change and preparation for the upcoming TPAUSE based delay variant. [ Kyung Min Park: Added __init to use_tsc_delay() ] Signed-off-by: Thomas Gleixner Signed-off-by: Kyung Min Park Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/1587757076-30337-2-git-send-email-kyung.min.park@intel.com

x86/asm: Fix MWAITX C-state hint value

2019-10-08T11:25:24+00:00

As per "AMD64 Architecture Programmer's Manual Volume 3: General-Purpose and System Instructions", MWAITX EAX[7:4]+1 specifies the optional hint of the optimized C-state. For C0 state, EAX[7:4] should be set to 0xf. Currently, a value of 0xf is set for EAX[3:0] instead of EAX[7:4]. Fix this by changing MWAITX_DISABLE_CSTATES from 0xf to 0xf0. This hasn't had any implications so far because setting reserved bits in EAX is simply ignored by the CPU. [ bp: Fixup comment in delay_mwaitx() and massage. ] Signed-off-by: Janakarajan Natarajan Signed-off-by: Borislav Petkov Cc: Frederic Weisbecker Cc: Greg Kroah-Hartman Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Thomas Gleixner Cc: "x86@kernel.org" Cc: Zhenzhong Duan Cc: Link: https://lkml.kernel.org/r/20191007190011.4859-1-Janakarajan.Natarajan@amd.com Signed-off-by: Ingo Molnar

x86/timer: Don't inline __const_udelay()

2019-04-19T15:49:47+00:00

LTO will happily inline __const_udelay() everywhere it is used. Forcing it noinline saves ~44k text in a LTO build. 13999560 1740864 1499136 17239560 1070e08 vmlinux-with-udelay-inline 13954764 1736768 1499136 17190668 1064f0c vmlinux-wo-udelay-inline Even without LTO this function should never be inlined. Signed-off-by: Andi Kleen Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20190330004743.29541-4-andi@firstfloor.org

Merge branch 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2018-01-30T21:01:09+00:00

Pull x86 cleanups from Ingo Molnar: "Misc cleanups" * 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86: Remove unused IOMMU_STRESS Kconfig x86/extable: Mark exception handler functions visible x86/timer: Don't inline __const_udelay x86/headers: Remove duplicate #includes